One of the squid was caught near Kagoshima prefecture and was alive at the time, while two were found dead in fishing nets which were placed off the coast of Shimane prefecture. All were caught in 2013, and a study about them was published in the journal Marine Biodiversity Records this week.

The size of the squid varied from 14 to 33 centimeters (5.5 to 13 inches), resembling the size of adult squid of other species. Giant squid, known as the world’s largest invertebrate, are known to grow to more than 10 meters (33 feet).

“This is the first time in the world that such young giant squid were found, and it has helped us understand what they are like this early in their life stage,” said museum researcher Toshifumi Wada. Researchers looked at their body shape and suckers among other parts, he said.

Adult giant squid live by themselves, but the fact that two juveniles were captured together in Shimane may suggest that they travel in groups early in their lives, Mr. Wada said.

The squid were captured by pure luck, and brought to the researchers by the fishermen who found the uniquely shaped cephalopods. The squid are scheduled to go on display at aquariums in Shimane and Kagoshima.